Disc brakes are widely used for slowing or stopping rotation of an object in motion. One application of a disc brake is an elevator system and, particularly, a traction-based elevator system. Such elevator systems generally include an elevator car connected to a counterweight through hoisting ropes trained around a traction sheave. The traction sheave is driven by a motor such that rotation of the traction sheave moves the hoisting rope, thereby causing desired movement of the elevator car. To slow or halt the motion of the elevator car (e.g., by actuating a brake), the traction sheave is connected to a disc brake.
The traction sheave can be coupled on each side with a flange that acts as a rotating disc or rotor of the disc brake. The traction sheave and the rotors rotate together to facilitate movement of the elevator car. When friction is applied against both sides of the rotors, the rotors, as well as the traction sheave slow down or halt, thereby slowing or halting the movement of the elevator car. Friction to the rotors is applied by a caliper having at least one set of brake pads, brake coils and springs on each caliper. When the brake is actuated, the brake coils are disengaged and the springs apply a force to the brake pads, which contact the rotors, creating tangential friction forces opposing the motion of the rotors and the traction sheave.
The caliper is mounted such that it is fixed in tangential and radial directions, but allowed to have some degree of translation, or float, in an axial direction relative to the rotors. Although this amount of float is necessary to allow correct braking operation under a range of axial motion and loads that are encountered in service, such float is nevertheless also responsible for off-centering the caliper relative to the rotors. Centering of the caliper and the rotors helps prevent the brake pads from contacting the rotors when the brake is released. Ideally, the caliper will be centered over the rotors at all times by itself with a uniform gap between each brake pad and the rotor braking surfaces of the rotors. However, this typically is not the case. Accordingly, several techniques have been proposed in the past to particularly center the caliper and to ensure that the brake pads do not contact the rotors when the brake is released.
Although effective, such traditional techniques nonetheless have several disadvantages. For example, in most traditional techniques, mechanical devices, such as, sensors are employed to center the caliper and the rotors. These sensors maintain substantial physical contact with the rotors, resulting in stictional and frictional losses. Often such techniques also require a power supply or other closed-loop system to operate, not only adding to the overall cost and maintenance of the disc brake, but also being prone to malfunction and shorter life spans. Additionally, such sensors may not accommodate differential thermal expansion between a mounting unit for the sensors and the rotors.
Accordingly, it would be beneficial if a reliable, robust and/or inexpensive system were developed to facilitate centering of the caliper relative to the rotors. It would additionally or alternatively be beneficial if such a system would minimize stiction and friction losses, accommodate any thermal expansions and/or eliminate the need for a separate power supply system.